Molecular cocrystals: design, charge-transfer and optoelectronic functionality

Abstract

Organic cocrystals, formed by a combination of electron-rich donors and electron-poor acceptors, play an important role in tailoring the optoelectronic properties of molecular materials. Charge transfer interactions in cocrystals not only endow them with an ordered three-dimensional (3D) supramolecular network in different constituent units, but also render them ideal scaffolds to control the intermolecular interactions in multicomponent solids. In this perspective, we firstly introduce preparation methods, molecular packing modes and charge transfer in organic cocrystals. Then, we focus on the novel and promising optoelectronic properties of organic cocrystals based on charge transfer interactions. Finally, we briefly discuss the outlook for the future development of these multicomponent crystalline materials.

Insights into the Control of Optoelectronic Properties in Mixed‐Stacking Charge‐Transfer Complexes

“…The photoresponsive behavior was further studied by exploring the photocurrent, and the corresponding phototransistor schematic is depicted in Figure a. Under white‐light illumination, significantly enhanced generation of photocarriers occurred in the TMCA‐based device with photocurrent on/off ratio [ P =( I light − I dark )/ I dark ] greater than 2×10 3 ( V G =16 V, Figure e), which is among the highest values for all reported organic cocrystals, and shifting of the onset voltage V on to the positive indicates a photovoltaic effect . In comparison, the TMFA‐based device exhibits much inferior photoresponse with decreased P value (≈500), whereas TMTQ shows loss of the photoresponse (Figure b and h), which is also evidenced by the output curves (Figure S24 in the Supporting Information).…”

“…Single-crystal XRD was performedt og ive insighti nto the molecular packinga nd driving forces fort he co-assembly process. Both TMFAa nd TMCA cocrystallize in space group P2 1 /c (monoclinic system) with unit-celld imensions of a = 15.872(3), b = 6.731(2), c = 21.563(7) , a = 90, b = 127.690 (19), g = 908 and a = 11.5873 (16), b = 6.8557(5), c = 24.8500 (19) , a = 90, b = 90.062(6), g = 908,r espectively (Table S1 in the Supporting Information). Although the replacement of halogenated substituents in acceptors results in as imilarc o-assembly mode, molecular packing and interactions are significantly affected.…”

Diphenylene‐Tetracyanoquinodimethane Cocrystals as Stable Organic Rectifiers

“…In recent years, the rectifying diode of inorganic semiconductor has possessed a more mature production technology and practical application, whereas it is difficult to continue to improve the performance, reduce the size and lower the cost resulting from the number of devices cannot grow indefinitely on per unit area . Meanwhile, the attentions on the organic electronics are increasing appreciably due to the superiority of marvellous flexible properties, extensive fabrication with mild conditions, cheap cost and simplicity of device fabrication . Organic semiconductor materials which mainly are conjugated organic molecules and conductive polymers at present are the core for achieving organic rectifier diode devices.…”

Thermally Activated Delayed Fluorescence in an Organic Cocrystal: Narrowing the Singlet–Triplet Energy Gap via Charge Transfer

“…This broad peak in TTC is atypical CT peak. [23] Theevident difference of the cocrystal and the constituent TCNB and TSB crystal is also found in the room-temperature (RT) emission spectrum. TTC has an ew,f eatureless broad peak (full width at half maximum (FWHM) = 116 nm) at l = 580 nm (Figure 1d), while TCNB and TSB both have blue emission at wavelengths lower than 400 nm (Supporting Information, Figure S2c).…”